It is known in the art relating to engine crankcase ventilation systems, including closed positive crankcase ventilation systems, to provide passage defining means for conducting vapors from the engine crankcase and the connected enclosed valve actuating area of the cylinder head to the engine induction system for mixing with the intake charge and burning in the cylinders. Many such systems in use have utilized an externally mounted valve and connecting conduit as shown, for example, in U.S. Pat. No.3,359,960 Pittsley, assigned to the assignee of the present invention. In such cases, the flow control, or positive crankcase ventilation, valve, generally referred to as a PCV valve, is commonly mounted upon the exterior of an engine outer wall, such as the engine valve (or rocker) cover, and therefore, is easily accessible for servicing or replacement.
It is also known, however, to provide a closed crankcase ventilation, or vapor recycling, system in which passages communicating the crankcase with the induction system are entirely within the engine so that external piping, hoses, and so forth are avoided. One example of such an arrangement, which additionally includes internal mounting of PCV valves for controlling crankcase ventilation flow, is shown in U.S. Pat. No. 3,241,534 Kennedy, also assigned to the assignee of the present invention. In the latter arrangement, the PCV valves are mounted in openings of the cylinder head upper walls communicating with some of the inlet ports and are located within the enclosed portions covered by the rocker (or valve) covers.
The Kennedy arrangement has the advantage of providing a clean appearing engine exterior and reducing the possibility of leaks occurring in the exposed hoses and conduits of the more common externally ducted systems; however, it has the shortcoming that the PCV valves are less accessible. To service or replace the valves of the Kennedy arrangement, the valve covers must first be removed to allow access to the upper cylinder head walls upon which the PCV valves are mounted. Also, in the latter arrangement, the direct connection of the crankcase and valve cover area with individual cylinder head intake ports, does not provide the same balance of distribution of the crankcase vapors to the various cylinder intake ports which can be accomplished by systems that distribute the vapors to a central opening of the manifold feeding all of the intake ports.